what is the precipitation?

recently  we need test one compound in plastic materials by LC-MS .the most challenge is that  how to extract the target compound from plastic materialsin our house method it described as follow :1.Polycarbonate (PC) extraction method
Dissolve the 1 g sample with 20 mL DCM (5.2.3), shake well until the sample totally dissolve, if thesample cannot completely dissolve, ultrasonic at 40oC for 60 minutes.
Re-precipitated the plastic with 100 mL acetone (5.2.4) with drop-wise and constant swirling.
Stand for 30 minutes to allow precipitate plastic residue.
2.Extraction method with others material
Add 20 mL  to 1 g sample and ultrasonic at 40oC for 60 minutes.
Re-precipitated the plastic with 100 mL ACN with drop-wise and constant swirling.
Stand for 30 minutes to allow precipitate plastic residue. Now  the qustion is why used  different extraction solvent for different material,and why precipitate plastic residue appeared  after adding ACN

Answers

  • Hi TIM,

    you need different solvents because it depends on the plastic you must dissolve.

    you dissolve the plastic in order to release the substances you want to analyze then you precipitate the plastic so that the molecules of the polymere can't interfere.

    Tetrahydrofuran dissolve PVC and acetonitrile precipitate it for example.

    I'm not sure I'm clear because my english is poor...

  • Well,your information is useful,thank you ! As your Said, dissolving the plastic is to release the analysis substance,but it still need proved which kind of solvent is better

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